In recent years the volume of information has grown rapidly. Utilization of electronic instruments has also increased significantly. As a result, personal computers, notebook computers, PDAs, and handsets are frequently used by the general public in their daily lives. For entering data into electronic instruments, keyboards or keypads are the most convenient input devices.
Because the number of the button keys on a keyboard is fixed, if a single key cannot provide the original function set for the key, a composite key is generally used to input information. As most users use their hands to operate the composite key to input, the fingers must be extended to cover a distance of at least two keys (a composite key) simultaneously to depress the keys. When the interval of the two keys is too large, the fingers are overextended. To operate the composite keys to enter information under such a condition for a long period of time can cause injury to the hands.
Nowadays the general public wants their electronic instruments be slim and light to make carrying easier. In order to meet these profile (slim and light) requirements, some functions are sacrificed. For instance, the size of the keyboard and number of the button keys are reduced. As a result, users cannot enter input information into the electronic instruments as fast as desired.
In view of the aforesaid problems, it is necessary to enable users to input information with fewer keys and prevent injury resulting from operating the composite keys.